clippy: clean up all warnings

Mostly `cargo clippy --fix`: needless borrows, redundant field names,
match -> if let, io::Error::other, Option::filter/map, let chains, c""
literals. By hand: drop unused impl lifetimes, a type alias for the
font preload map, Iterator::find in next_buffer, contains_key, and
allow new_ret_no_self where constructors intentionally return the
boxed/generic wrapper type.

No functional change; tests and release build unchanged.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/widgets/launcher.rs

@@ -120,7 +120,7 @@ impl Prompt {
     }
 
     fn append(&mut self, v: &str) {
-        if self.input.len() == 0 {
+        if self.input.is_empty() {
             match v {
                 "!" => {
                     self.mode = PromptMode::Shell;
@@ -271,7 +271,7 @@ impl Launcher {
 
         Launcher {
             next_token: None,
-            options: options,
+            options,
             matches: Vec::new(),
             launch_cmd,
         }
@@ -354,7 +354,7 @@ impl InterfaceWidget for Launcher {
             .auto_draw_text_with_cursor(
                 &mut prompt_line,
                 fg,
-                &format!("   {}", &intf.prompt.input),
+                &format!("   {}", intf.prompt.input),
                 intf.prompt.cursor + 3,
             )
             .unwrap();
@@ -474,7 +474,7 @@ impl InterfaceWidget for Shell {
             .auto_draw_text_with_cursor(
                 &mut prompt_line,
                 fg,
-                &format!("   {}", &intf.prompt.input),
+                &format!("   {}", intf.prompt.input),
                 intf.prompt.cursor + 3,
             )
             .unwrap();
@@ -531,7 +531,7 @@ impl Calc {
 
         let old = self.old.lock().unwrap();
         for (input, res) in old.iter() {
-            write!(f, "{}={}\n", input, res).unwrap();
+            writeln!(f, "{}={}", input, res).unwrap();
         }
         f.sync_data().unwrap();
     }
@@ -567,10 +567,7 @@ impl InterfaceWidget for Calc {
             rcalc_lib::parse::eval(&intf.prompt.input, &mut rcalc_lib::parse::CalcState::new())
                 .map(|x| format!("{}", x))
                 .map_err(|x| format!("{}", x));
-        self.result = match res {
-            Ok(v) => Some(v),
-            Err(_) => None,
-        };
+        self.result = res.ok();
     }
 
     fn draw(
@@ -593,7 +590,7 @@ impl InterfaceWidget for Calc {
         font.auto_draw_text_with_cursor(
             &mut prompt_line,
             fg,
-            &format!("   {} ", &intf.prompt.input),
+            &format!("   {} ", intf.prompt.input),
             intf.prompt.cursor + 3,
         )
         .unwrap();
@@ -712,7 +709,7 @@ impl Interface {
     }
 
     fn exit(&mut self) {
-        if self.inner.prompt.input.len() == 0 {
+        if self.inner.prompt.input.is_empty() {
             std::process::exit(0);
         }
 
@@ -810,7 +807,7 @@ impl Widget for Interface {
     }
 
     fn geometry_update(&mut self, _fonts: &mut FontMap, geometry: &Geometry) -> Geometry {
-        self.inner.geometry = geometry.clone();
+        self.inner.geometry = *geometry;
         self.inner.geometry
     }